COMPARATIVE STUDY BETWEEN CHEMICAL AND NON-CHEMICAL CONTROL AGAINST Sclerotium cepivorum, THE CASUAL WHITE ROT OF ONION UNDER EGYPTIAN CONDITIONS.

Abstract

Sclerotium cepivorum one of the most destructive soilborne pathogens affecting onion and other Allium species and causing considerable damage to the host under congenial environments. In this work, it was isolated from North Egypt; many attempts were done to control onion white rot disease caused by the pathogen. Three fungicides; procimidone (sumisclex®25), vinclozolin (Ronilan) and tolclofos-methyl (Rizolex) were used against S. cepivorum and compared with a some biological non-chemical treatments. These treatments include a five antagonistic fungi, two antagonistic bacteria, three essential oils and three plant extracts. Among all fungicides tested, it was found that procymidone application was the best chemical treatment giving 100% inhibition in mycelial growth and reduction of sclerotia germination at all concentrates tested, in-vitro. While, T. harzianum was the best antagonistic fungi against the pathogen giving 82.8% reduction. On the other hand, Pseudomonas fluorescensand Bacillus subtilis have achieved complete inhibition of mycelial growth giving 100 and 94.00%, respectively and suppressed completely sclerotial germination when exposed to bacterial culture in half-strength Nutrient Broth (NB). Among all tested essential oils, it was noticed that, cinnamon (Cinnamomum zeylanicum) was the best essential oil for reducing mycelial growth giving 100% at 0.50 and 0.75%.While the cinnamon extract was the best against S. cepivorum with 94.40% inhibition in mycelial growth at 50% concentrate and completely suppressed sclerotial germination. Conversely, onion white peels extract gave the lowest rate of mycelium growth reduction giving (11.11%) and stimulated sclerotial germination than other extracts.